Click on a square to move the square, or row of squares into the empty space. To do the puzzle, click "Scramble." The objective of the puzzle is to put it back the way it was when the page loaded. There will be no sights or sounds indicating that "You Solved It," or saying "You WON!!!" You are intelligent enough to know whether you've solved the puzzle.
This is one of the first mechanical puzzles I learned to solve. It was quite famous in its day. Try putting the board into other configurations. This puzzle works exactly like the original game. There is no preferred configuration, or no special winning configuration.
You will discover that the mirror-image configuration is impossible to achieve. I believe that this is because the movements of the squares all represent even permutations, and to achieve the mirror image you must do an odd permutation. Regardless, the transformations do not generate the entire symmetric group, so there are configurations that cannot be achieved.